1. Field of the Invention
This invention relates to a steel-material. shearing machine which is mounted at the end of the arm of work machines such as a power shovel to shear various steel materials.
2. Prior Art
There exist similar kinds of shearing machines, for instance, such as disclosed in the Japanese Patent Public Disclosure [KOKAI] No. 62-271619. As shown in FIG. 12, shearing machines of this kind are equipped with a lower jaw 2 at the end of an arm 1, and an upper jaw 3 is pivoted at the lower jaw 2 by a pivot shaft 4; said upper jaw 3 is operated by a hydraulic cylinder 5 located on the arm 1. The upper jaw 3 is moved against the lower jaw 2 to shear steel materials between the lower jaw 2 and upper jaw 3.
There are other crushing machines for shearing steel materials such as disclosed in the Japanese Patent Public Disclosure [KOKAI] NO 2-232470. A shearing machine of this kind is equipped with a supporting frame 7 to which the centers of a lower jaw 2 and upper jaw 3 are pivoted by shafts 8 as shown in FIG. 13. A hydraulic cylinder 9 is linked to each of the rear end of the lower jaw 2 and upper jaw 3 to nip and shear steel materials between them.
The steel-material shearing machines of the former category cannot change its direction easily since the lower jaw 2 is fixed at the end of the arm 1. In addition, because only the upper jaw 3 is moved, the opening angle is small, and its movement is slow. Furthermore, a large hydraulic cylinder is necessary in order to generate a large force.
The steel-materials shearing machines of the latter category require an inefficient working process because shearing position is fixed, and steel materials must be placed on the right position. In addition, the lower jaw 2 and upper jaw 3 do not cope with twisting. Therefore, shearing may not be completed well because of a gap between the lower jaw 2 and upper jaw 3 due to a large twisting force.